X-ray generating apparatus and X-ray fluoroscopyimaging system equipped with the same

ABSTRACT

The present invention provides an X-ray generating apparatus and an X-ray fluoroscopy imaging system comprising the same. The X-ray generating apparatus comprises: an electron accelerator, an electron emission unit, and a target; and a shielding and collimating device, including a shielding structure and multiple collimators arranged in the shielding structure, wherein the collimators are thin gaps extending from the target to an exterior surface of the shielding structure and having an axis transverse an electron beam shooting the target, and at least two collimators forming different angles with the electron beam are arranged on the same side of a plane contains the electron beam shooting the target, and the planes where the collimators locate form angles from 30 degrees to 150 degrees with the electron beam shooting the target, to draw out planar beams having different draw-out angles, each having uniform intensity distribution in its respective plane.

This application is a continuation of U.S. application Ser. No.14/582,060, filed Dec. 23, 2014, which claims priority to Chinese PatentApplication No. 201310741400.3, filed on Dec. 30, 2013, which is herebyincorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to an apparatus for generating an X-raybeam, and more specifically, to an apparatus for generating a planarfan-shaped high energy X-ray beam having a uniform intensitydistribution using a high energy electron accelerator.

BACKGROUND OF THE INVENTION

X-rays radiation has wide applications in industry nondestructivetesting, security inspection and other domains. For large objects to betested, e.g., boilers, airspace engines, mass cargoes atairports/railway stations/customs, high energy X-rays are required fortheir fluoroscopy examinations, generally produced by electronaccelerators at energies above 2 MeV. The basic way of producing X-raysby an electron accelerator is as follows: producing an electron beamwith an electron gun, accelerating the electron beam by an electricfield to obtain high energy, shooting a target by the high energyelectron beam to produce X-rays. X-rays produced by the electron beamshooting on the target generally distribute in various direction at a 4πsolid angle. X-rays produced by electron beams with different energiesshooting on a target may have different intensity distributions invarious radiation directions. In general, the higher energy an electronbeam has, the higher intensity the forward X-rays have, and the lowerintensity the X-rays in the other directions have. With a target pointas the center and X-ray intensity in various directions as amplitude,the X-ray intensity has a “pine core shaped” distribution over solidangles as shown in FIG. 3. In various X-ray fluoroscopy imaging systems,instead of adopting all X-rays over the 4π solid angle, only a smallportion is adopted. In many situations, X-rays in a planar fan-shapedarea are used, such as a sliced “planar fan-shaped beam”. As shown inFIG. 2, such a system is composed by a high energy electron accelerator,a shielding and collimating device, a detector and a signal analysis andimage processing system, with dotted arrows schematically showing a“planar fan-shaped beam”. “Planar fan-shaped beams” have wideapplications in high energy industry CT, container inspection systems,vehicle inspection systems, train fluoroscopy examination systems, aircargo inspection systems, luggage and parcel inspection systems and thelike.

In existing methods for obtaining a “planar fan-shaped beam” in theprior art, a “thin gap” shielding collimator is arranged in front of thetarget of the high energy electron accelerator to shield X-rays in mostof directions while only passing X-rays through the “thin gap” to form a“planar fan-shaped beam”. In general, the “thin gap” is arrangeddirectly in front of the target, and on the advancing direction of theshooting electron beam, which is referred to as “zero degree” directionherein. The highest intensity of X-rays produced by electronaccelerators is used in the prior art. However, there are largedifferences between X-ray intensities in different directions in the fanarea. Taking a 9 MeV accelerator as an example, the X-ray intensity inthe zero degree direction of the fan area is 10 times of that in the45-degree direction at the edge. After many years of development of theX-ray fluoroscopy imaging system shown in FIG. 2, there is a greatimprovement on the performance of the detector, and the demand for theintensity of X-rays has been significantly reduced. However, in order toimprove image quality, there is an increasing requirement for thequality of X-rays. For example, a ratio of intensity differences ofX-rays in various directions in the fan area, of less than 2, i.e., a“planar fan-shaped beam having uniform intensity”, is desired.

SUMMARY OF THE INVENTION

The present invention has been proposed to solve one of the aboveproblems. An object of the present invention is to provide an apparatusfor generating a high energy planar fan-shaped X-ray beam having uniformintensity to meet the requirement of the development of X-rayfluoroscopy imaging system technologies.

The present invention provides an X-ray generating apparatus,characterized in comprising:

a high energy electron accelerator including an electron accelerationunit, an electron emission unit mounted on one end of the electronacceleration unit, and a target mounted on the other end of the electronacceleration unit; and

a shielding and collimating device, including a shielding structure anda collimator arranged in the shielding structure,

wherein the target is surrounded by the shielding structure and is shotby an electron beam coming from the electron emission unit andaccelerated by the electron acceleration unit to generate X-rays,

the collimator is arranged in a direction forming an angle from 30degrees to 150 degrees with the electron beam shooting the target andpassing through the target point.

Said one end of the electron acceleration unit refers to theacceleration starting position of the electron acceleration unit, andthe other end of the electron acceleration unit refers to theacceleration ending position of the electron acceleration unit.

Further, in the X-ray generating apparatus of the present invention, theelectron accelerator has energy of above 2 MeV.

Further, in the X-ray generating apparatus of the present invention, thecollimator is a planar fan-shaped gap arranged in the shieldingstructure.

Further, in the X-ray generating apparatus of the present invention, theelectron accelerator further comprises an electron drift segmentconnected between the electron acceleration unit and the target.

Further, in the X-ray generating apparatus of the present invention, theelectron drift segment is a small diameter conduit, wherein the smalldiameter conduit has an inner diameter larger than the diameter of theelectron beam and an outer diameter less than the outer diameter of theelectron acceleration unit.

Further, in the X-ray generating apparatus of the present invention, theshielding structure is made from a material that is able to block andabsorb most of undesired X-rays; the target is a planer structure, aspherical surface structure or other curved surface structure.

Further, in the X-ray generating apparatus of the present invention, theshielding and collimating device has multiple collimators, the positionsof which are symmetrical with respect to a plane passing the targetpoint and perpendicular to the electron beam or are symmetrical withrespect to the electron beam.

The present invention provides an X-ray fluoroscopy imaging system,characterized in comprising the X-ray generating apparatus describedabove.

The present invention mainly provides an apparatus for generating a highenergy planar fan-shaped X-ray beam having uniform intensity. Theapparatus for generating a high energy planar fan-shaped X-ray beamhaving uniform intensity of the present invention is composed of a highenergy electron accelerator with an energy of above 2 MeV and ashielding and collimating device, wherein the collimator is arranged ina direction forming an angle in a range from 30 degrees to 150 degreeswith the electron beam shooting the target, and the number of thecollimators may be one or more than one.

In the present invention, by means of arranging the collimator in adirection forming a lager angle with the direction of the electron beamshooting the target, a X-ray beam may be obtained with better quality,such as (1) more uniform intensity of X-rays in various directionswithin a fan area on a plane; (2) smaller energy dispersion of X-rayswithin the fan area on the plane; and (3) a smaller size of target pointwith the projection point of X-rays on the plane being the target point.These three properties may improve the image quality of the X-rayfluoroscopy imaging system. Due to better uniformity of X-rays, X-raysmay be drawn out at a large angle to increase X-ray coverage within acloser distance. Multiple collimators are arranged in the shielding andcollimating device with different angle and position relationships, soas to realize: (1) obtaining multi-angles-of-views images from multipleangles of views; (2) obtaining double-energy effect by means ofgenerating X-ray beams with different energy quantities from differentcollimators, so as to determine materials of objects under inspection;(3) implementing a double-channel inspection system using oneaccelerator to improve the inspection speed of the X-ray fluoroscopyimaging system and its cost performance; and a combination thereof toform a X-ray fluoroscopy imaging system in different combinations ofdouble channel/high energy/multiple angles of views.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an X-ray generating apparatus of thepresent invention;

FIG. 2 is a schematic diagram of a planar fan-shaped high energy X-raybeam fluoroscopy imaging system;

FIG. 3 is a schematic diagram of an intensity distribution of X-raysproduced by a high energy electron accelerator at different angles (in apine core shape);

FIG. 4 shows planar X-ray beams obtained from collimators in differentplanes, (A) a X-ray beam on plane A; (B) a X-ray beam on plane B; (C) aX-ray beam on plane C;

FIG. 5 is a schematic diagram of a sectional structure of the collimatoron plane B shown in FIG. 4;

FIG. 6 is a schematic diagram of X-ray target point in differentprojection sizes when collimators are arranged on different planes;

FIG. 7 is a schematic diagram of three target structures in differentshapes, (A) planar target, (B) spherical surface target, and (C) Lshaped target;

FIG. 8 is a schematic diagram of shielding and collimating devices withdifferent structures.

DETAILED DESCRIPTION OF THE EMBODIMENT

Below, the present invention will be described in detail with referenceto the drawings.

FIG. 1 is a schematic diagram of an apparatus for generating a planarfan-shaped high energy X-ray beam having uniform intensity of thepresent invention. The apparatus for generating a planar fan-shaped highenergy X-ray beam having uniform intensity of the present inventioncomprises high energy electron accelerator 1 and shielding andcollimating device 2, wherein the high energy electron accelerator 1comprises electron emission unit 101, electron acceleration unit 102 andtarget 103; the shielding and collimating device 2 comprises shieldingstructure 201 and collimators 202; the target 103 is surrounded by theshielding and collimating device 2, and the collimator 202 is arrangedin a direction passing through the target point and forming an anglefrom 30 degrees to 150 degrees with an electron beam shooting thetarget.

Further, the electron accelerator 1 has energy of above 2 MeV (MillionElectron Volt). The electron accelerator 1 is used to produce a highenergy electron beam E, and in general comprises electron emission unit101, electron acceleration unit 102 and target 103. The electronaccelerators are widely used devices, including high voltageaccelerators, induction accelerators, cyclotrons, linear accelerators,etc. The principle of the electron accelerators is as follows: with theoperation of its power supply and control systems, the electron emissionunit produces an initial electron beam E, which enters into the electronacceleration unit and is accelerated by a high voltage field, inductionfield, or microwave field to obtain high energy. The high energyelectron beam E then bombards the target to produce X-rays in variousdirections with a 4π solid angle. In general, the moving direction ofthe electron beam E is defined as the forward direction. X-rays producedby the high energy electron beam E shooting the target have differentintensity values in different directions, with a maximum value in theforward direction, and gradually reduced values as increasingly apartfrom the forward direction. The higher energy the electron beam has, themore apparent this variation becomes. For example, for X-rays producedby a 9 MeV electron beam shooting the target, if the intensity ofcentral X-rays (in the forward direction) is defined as 100%, theradiation intensity is about 73% in a direction apart from the centerdirection by 5 degrees, about 53% in a direction apart by 10 degrees,about 40% in a direction apart by 15 degrees, about 18% in a directionapart by 30 degrees, about 10% in a direction apart by 45 degrees, about7% in a direction apart by 60 degrees, about 5% in a direction apart by90 degrees, and about 4% in a direction apart by 120 degrees, showing anapparent forward-direction centralized distribution. This distributionis axially symmetric with respect to the moving direction of theelectron beam. With a position (referred to as a target point) shot bythe electron beam as the center, FIG. 3 shows a graph of a 3Ddistribution of X-ray intensities at various angles on variousdirections within a 4π solid angle, just like a pine core and thusreferred to as a “pine core shape”. In FIG. 3, the electron beam Eshoots the target to produce X-rays radiated in various directions atthe target point. The X-rays have a 3D intensity distribution in a pinecore shape. “X-Y-Z” are coordinate axes of the 3D distribution. A “X-Y”plane is defined as the horizontal plane, and other three planes A, B, Care observation planes perpendicular to the horizontal plane and formingdifferent angles with the electron beam E.

With the target point as the center and cutting the “pine core shape”with planes forming different angles with the shooting electron beam E,different sectional diagrams are obtained, showing 2D intensitydistributions of X-rays on those planes at different angles, as shown inFIG. 4.

FIG. 4(A) shows an X-ray intensity distribution at different angles onplane A of FIG. 3. Since the plane A forms a zero degree angle with theelectron beam E, the electron beam E may be observed on the plane A. Theelectron beam E shoots the target and produce X-rays radiated at variousangles at the target point position o, wherein the X-ray intensity inthe forward direction (the moving direction of the electron beam) hasthe maximum value, the larger angle a direction deviates from the zerodegree direction, the smaller intensity the X-rays have in thatdirection. On the plane A, X-ray intensities in various directions havethe largest difference in the distribution. For example, for a 9 MeVelectron beam E, the X-ray intensity in the 0° direction is 10 times ofthat in the 45° direction and 20 times of that in the 90° direction.

FIG. 4 (B) shows an X-ray intensity distribution at different angles onplane B of FIG. 3. The plane B forms an angle between 0° to 90°, e.g.,45°, with the electron beam E. Although the electron beam E cannot beobserved on this plane, still with the position o at which the electronbeam E shoots the target as the center, X-rays produced by the electronbeam E shooting the target radiate at various angles from the targetpoint position o. Also, the intensity on the X-Y plane is the maximum,and is defined as a 0° direction. The larger angle a direction derivesfrom the 0° direction on the plane B, the smaller intensity the X-rayshave. However, because the largest X-ray intensity on the plane B is theintensity in a direction with an angle between the plane B and theelectron beam E in the “pine core shaped” X-ray intensity distribution,for example, the intensity at the 45° direction, it is far less thanthat in the 0° direction on plane A. There are smaller differencesbetween X-ray intensity distributions in various directions on the planeB.

FIG. 4 (C) shows an X-ray intensity distribution at different angles onplane C of FIG. 3. The plane C forms a 90° angle with the electron beamE. the shooting electron beam E is perpendicular to the plane C, stillwith the position o of shooting target as the center, X-rays produced bythe electron beam E shooting the target radiate at various angles fromthe target point position. Intensities are consistent in variousdirections, equivalent to the intensity in the 90° direction in the“pine core shaped” distribution. There is not any difference betweenX-ray intensities in various directions on the plane C.

X-rays produced by an electron beam E shooting a target with energy Eare in a continuous energy spectrum with energy from 0 to E. For X-rayshaving different energy quantities, their angle distribution complieswith a certain rule, i.e., X-rays having higher energy are mostlydistributed in the forward direction and in a range of smaller angles.The larger a direction derivates from the 0° direction, the loweraverage energy X-rays have in that direction. A detailed descriptionabout relevant characters of spectrum distribution may be found intechnical documents of electron accelerator technology, high energyphysics and so on. X-ray spectrum distributions obtained on observationplanes other than planes A, B, C described above are similar to theintensity distributions shown in FIG. 4 (A), (B), (C), i.e., the higherintensity an angle corresponds to, the higher energy X-rays have at thatangle.

The shielding and collimating device 2 comprises shielding structure 201and collimators 202. The shielding structure 201 is made from a high Zmaterial (i.e., high atomic number material), such as lead, tungsten,depleted uranium, for blocking and absorbing (i.e., shielding) most ofundesired X-rays. X-rays comply with an exponential decay rule whenpassing through an object. The larger atomic number the object has orthe higher density it has, the faster the X-rays decay. Thus, ingeneral, the shielding structure 201 is made from a high Z material,such as a combination of one or more of lead, tungsten, and depleteduranium to block and absorb undesired X-rays. Because X-rays produced bya high energy electron beam shooting a target has a “pine core shaped”intensity distribution, the amounts of X-ray intensity to be blocked atdifferent angles are different. So, the shielding structure hasdifferent thickness in different directions, generally like a “pine coreshape”. Commonly, for the simplicity of fabrication and saving material,the shielding structure 201 is an axisymmetric structure, with themoving direction of the shooting electron beam as its axis of symmetry,having thickness in various directions corresponding to the radiationintensity, and with a contour approximated by steps. Certainly, theshielding structure 201 may be in any other form, so long as the effectof shielding undesired X-rays may be produced and the requirement forthe smallest thickness in various directions can be satisfied.

Further, the shielding and collimating device 2 comprises shieldingstructure 201 and collimators 202. The collimator 202 is a thin gap in aplanar fan shape provided in the shielding structure 20 for drawing outX-rays to be used and confining the X-rays in a desired planar shape.The center of the fan is the target point o where the electron beamshoots the target. The thickness of the thin gap is in the order ofmillimeters, in general 0.5 mm to 5 mm, typically 2 mm, for example.Further, the thin gap may be a gap with a certain taper, for example, itmay has a thinner thickness closer to the target point o and a thickerthickness apart from the target point o, for example, 1.5 mm at thetarget point, 2 mm at a middle portion, and 2.5 mm at the outlet of thegap. The collimator 202 confines the shape of the X-rays, comprising:defining the planar thickness of the X-rays by the thickness of the thingap of the collimator 202; defining an emission angle range in the planeof the X-ray beam by the fan angle of the collimator 202, for example,90°; defining the relative position of the center of the X-ray beam inthe fan angle range by the position of the fan angle of the collimator202 with respect to the “X-Y” horizontal plane, for example, the centerof the X-ray beam is at 0°, the fan angle ranges from −30° to 60°, andtotally opening angle of 90°. A sectional structure of the shielding andcollimating device is shown in FIG. 5 is shown in FIG. 5, correspondingto a situation in which the collimator is located on plane B in FIG. 3and the center is the target point o. The target point is surrounded bythe solid shielding structure 201 to block and absorb undesired X-rays.The collimator 202 is a gap in a planar fan shape for drawing out X-raysto be used, and the fan has a center at 0° and has a 90° opening anglefrom −45° to +45°. Generally, for the convenience of processing, theshielding and collimating device 2 is divided into several parts forprocessing and then the processed parts are assembled. For example, theshielding and collimating device 2 is divided along the positions on thecollimators 202, or is divided along the periphery of the collimators202. Generally, the parts of the shielding structure 201 could beprocessed in a lower precision while the parts of the collimators 202shall be processed in a higher precision and/or by using anothermaterial. Then, these parts are assembled into the shielding andcollimating device 2. As a result, the shielding and collimating device2 could be an integral structure, or it could be an assembled structurewith multiple parts, for example, a structure in which the shieldingstructure is separate from the collimators.

In the present invention, the collimator 202 is characterized by formingan angle ranging from 30° to 150° between a plane where it locates andthe electron beam E. As described above, in the prior art, thecollimator is arranged directly in front of the target (at 0° or nearly0°) to obtain a planar fan-shaped X-ray beam, as shown in plane A inFIG. 3, so that X-rays having the highest intensity and energy arelocated in the planar fan. However, with the development of existingtechnology, on one hand, it is very easy to realize a powerful X-raybeam using an industry high energy electron accelerator, for example,Hextron 3000 available from Nuctech Company Limited, under X-ray energyof 9 Mev, allowing a X-ray intensity of 3000 Rad/m·min at 0°, 540Rad/m·min at 30°, and even 150 Rad/m·min at 90°, 120 Rad/m·min at 150°.On the other hand, the requirement for X-ray intensity in X-rayfluoroscopy imaging systems is constantly falling down. For example, invarious types of products of large container inspection systemsmanufactured by the Nuctech Company Limited, only X-ray intensity ofseveral or hundreds Rad/m·min is required. Thus, the intensity of planerfan-shaped X-ray beams obtained through arranging a collimator at alarge angle such as plane B and plane C shown in FIG. 3 may completelymeet the application requirement of existing products.

Through arranging collimators at large angles, planar fan-shaped X-raybeams obtained as such have better uniformity. As described above, asshown in FIG. 4, three collimators are arranged on planes A, B and Crespectively to obtain X-ray beams, for all of which the “X-Y”horizontal plane is the 0° direction. In a fan area from −45° to +45°(90° in total), a planar fan-shaped X-ray beam obtained from thecollimator on plane A has a central intensity that is 10 times of itsedge intensity, a planar fan-shaped X-ray beam obtained from thecollimator on plane B has a central intensity that is 2 times of itsedge intensity, and a planar fan-shaped X-ray beam obtained from thecollimator on plane C has a consistent intensity in various directions.

A planar fan-shaped X-ray beam obtained through arranging a collimatorat a large angle has a spectrum character similar to its intensitycharacter. In general, the larger angle between the plane where thecollimator locates and the electron beam E, the lower average energy (orintegrable energy) the X-ray beam has. Therefore, the X-ray spectrumcharacter may be chosen deliberately through selecting the arrangementangle of the collimator.

For a planar fan-shaped X-ray beam obtained through arranging acollimator at a large angle, in terms of focus size of X-rays in theplane thickness direction, the projection has a smaller size. Theelectron beam E shoots the target and produces X-rays. The focus size ofX-rays is the geometric distribution of the electron beam E, in general,a circle with a diameter Φ. Planar fan-shaped X-ray beams obtained fromcollimators at different angles have different focus sizes in the planethickness direction. As shown in FIG. 6, FIG. 6(A) shows that the X-rayfocus size in the plane thickness direction is Φ when X-rays are drawnout from the collimator in the directly forward direction, which isequivalent to observing in the 0° direction. FIG. 6(B) shows that theX-ray focus size in the plane thickness direction is Φ*sin 45°, i.e.,about 0.7Φ, when the X-rays are drawn out from the collimator in the 45°direction, which is equivalent to observing in the 45° direction. FIG.6(C) shows that the X-ray focus size in the plane thickness direction isΦ*sin 60°, i.e., about 0.5Φ, when the X-rays are drawn out from thecollimator in the 60° direction, which is equivalent to observing in the60° direction. In a fluoroscopy imaging system using X-rays, the smallerthe focus size is, the higher resolution an obtained image has. Thusarranging the collimator at a larger angle is helpful to reduce thefocus size and thus improve image quality of the X-ray fluoroscopyimaging system.

In the apparatus for generating a planar fan-shaped high energy X-raybeam having uniform intensity of the present invention, the target 103may have a planar structure, a spherical surface structure, or othercurved surface structure. As shown in FIG. 7, a structure schematicdiagram of three targets in different shapes is shown. FIG. 7 (A) showsa planar target, FIG. 7 (B) shows a spherical surface target, and FIG.7(C) shows an L-shaped target. Targets in different shapes may producedifferent effects in geometry on the focus of a planar fan-shaped X-raybeam drawn out from collimators arranged at different angles. It isadvised in the present invention to flexibly select the target structureto adapt to different particular applications.

In the apparatus for generating a planar fan-shaped high energy X-raybeam having uniform intensity of the present invention, the high energyelectron accelerator 1 further comprises electron drift segment 104connecting the electron acceleration unit 102 and the target 103. Theelectron drift segment 104 is a small diameter conduit, wherein theelectron drift segment 104 has an inner diameter larger than thediameter of the electron beam E and an outer diameter far less than theouter diameter of the electron acceleration unit 102. In the electronaccelerator 1, the electron acceleration unit 102 generally has a largersize. When the target 103 is mounted at an end of the electronacceleration unit 102, on one hand, for shielding undesired side-backX-rays (larger than 90°) in the side-back direction, in order toguarantee that the shielding material has an enough thickness on itsshielding path, the shielding structure 201 will have a larger size,causing higher cost; on the other hand, due to the blocking of theelectron acceleration unit 102, it is difficult to draw out useful X-raybeams from the side-back direction for fluoroscopy imaging operation.Through arranging the electron drift segment 104 between the electronacceleration unit 102 and the target 103 to extend the target by a smalldiameter conduit, as shown in FIG. 1, on one hand, shielding may beeasily realized with the reduced volume and cost of the shieldingstructure 201; on the other hand, it is allowed to draw out a planarfan-shaped X-ray beam from a direction larger than 90°.

In the apparatus for generating a planar fan-shaped high energy X-raybeam having uniform intensity of the present invention, there may be oneor more collimators 202 arranged in a range from 30° to 150° to draw outone or more planar fan-shaped high energy X-ray beams having uniformintensity. FIG. 8 shows examples of arranging one or more collimators ofthe present invention.

FIG. 8 (A) shows an example of arranging a collimator in a directionforming nearly 90° with the electron beam E to draw out a planarfan-shaped high energy X-ray beam with almost consistent intensity atvarious angles and having a very small focus size in the thicknessdirection of the fan plane of the X-ray beam. This apparatus forgenerating a planar fan-shaped high energy X-ray beam having uniformintensity may be adopted in regular X-ray fluoroscopy imaging systems,which is beneficial to improve imaging consistency at various angles andincrease the resolution in the moving direction of the object and thusimprove image quality.

FIG. 8 (B) shows arranging two collimators on the same side of theelectron beam E to draw out two planar fan-shaped high energy X-raybeams, each having relatively uniform intensity distribution in itsrespective plane, wherein these two X-ray beams have different draw-outangles. The collimator 202 a forms an angle θ1 with the electron beam E,and the collimator 202 b forms an angle θ2 with the electron beam E,θ1≠θ2. This apparatus for generating two planar fan-shaped high energyX-ray beams having uniform intensity and different angles of views onthe same side may be adopted in double-angles-of-views X-ray fluoroscopyimaging systems (a fluoroscopy imaging technology of obtaining 3Dinformation using double-angles-of-views X-ray fluoroscopy imagingsystems has been disclosed in several patents of the Nuctech CompanyLimited), and may increase inspection speed and form a radiographicimage with 3D information. Through the use of the apparatus of thepresent invention, image quality of the system may be improved.

FIG. 8 (C) shows an example of arranging two collimators in a directionforming an angle less than 90° with the electron beam E and in adirection forming an angle larger than 90° with the electron beam E,respectively, to draw out two planar fan-shaped high energy X-ray beamshaving relatively uniform intensity distribution in their respectiveplanes, wherein the two X-ray beams have a significant energy differencetherebetween. The collimator 202 a forms an angle θ1<90° with theelectron beam E and draw out an X-ray beam having higher integrableenergy; and the collimator 202 b forms an angle θ2>90° with the electronbeam E and draw out a X-ray beam having lower integrable energy. Thisapparatus for generating two planar fan-shaped high energy X-ray beamshaving uniform intensity and different energy on the same side may beused in double-energy X-ray fluoroscopy imaging systems (advantages andapplications of the double-energy technology have been disclosed inseveral patents of the Nuctech Company Limited), capable of obtaining ashape and structure image of an object under inspection and recognizingits component material. Thus, a double-energy inspection effect may berealized using a conventional single-energy electron accelerator as aradiation source. Compared with existing schemes in which adouble-energy electron accelerator must be used as a radiation source,system complexity is lowered and cost is saved.

FIG. 8 (D) shows an example of arranging, respectively, two collimatorssymmetrically on both sides of a plane perpendicular to the electronbeam E to draw out two planar fan-shaped high energy X-ray beams havingrelatively uniform intensity distribution in their respective planes,wherein the two X-ray beams have a significant energy differencetherebetween and form symmetrical angles of views with respect to theobject under inspection. The collimator 202 a forms an angle θ1<90° withthe electron beam E and draw out a X-ray beam having higher integrableenergy; and the collimator 202 b forms an angle θ2>90° with the electronbeam E and draw out a X-ray beam having lower integrable energy,θ1+θ2=180°. This apparatus for generating two planar fan-shaped highenergy X-ray beams symmetrical with respect to the 90° direction havinguniform intensity and different energy on the same side may be used indouble-energy/double-angles-of-views X-ray fluoroscopy imaging systemsto realize X-ray fluoroscopy imaging system capable of achievingmultiple-layer imaging and material reorganization using oneconventional high energy single energy electron accelerator as aradiation source.

FIG. 8 (E) shows an example of arranging two collimators on both sidesof the electron beam E and symmetrically with respect to the electronbeam E to draw out two planar fan-shaped high energy X-ray beams havinga relatively uniform intensity distribution in their respective planes.These two X-ray beams have the same characters, such as spectrumcharacters, focus size, radiation intensity, angle distribution and soon. The collimator 202 a forms a “positive” angle θ1 with the electronbeam E, the collimator 202 b forms a “negative” angle θ2 with theelectron beam E, and θ1+θ2=0. This apparatus for generating two X-raybeams with identical characters on two sides may be used in adouble-channel X-ray fluoroscopy imaging system, so that the processingcapability of the X-ray fluoroscopy imaging system using an electronaccelerator as the radiation source may be doubled, while the system'simage quality is improved.

FIG. 8 (F) shows an example of arranging multiple collimators on bothsides of the electron beam E to draw out multiple planar fan-shaped highenergy X-ray beams having a relatively uniform intensity distribution intheir respective planes. These multiple X-ray beams have a variety ofcharacters, respectively, such as identical intensity distribution intheir planes, or low energy, or high energy, or small focus size, ordifferent angles of views. The collimator 202 a forms angle θ1 with theelectron beam E, the collimator 202 b forms angle θ2 with the electronbeam E, the collimator 202 c forms angle θ3 with the electron beam E,and the collimator 202 d forms angle θ4 with the electron beam E,wherein there is some relationship between θ1, θ2, θ3, θ4, or they areindependent with each other. The number of collimators may be also morethan four. This apparatus for generating multiple X-ray beams on twosides may be used in an X-ray fluoroscopy imaging system havingfunctions in a combination ofdouble-energy/double-angles-of-views/double-channel.

Note that, as to the multiple collimators of the present invention,their gaps for defining the shapes of the fan shaped X-ray beams mayhave the same or different thickness.

Note that, as to the multiple collimators of the present invention,their fan opening angles for defining the shapes of the fan shaped X-raybeams may be the same or different.

Note that, as to the multiple collimators of the present invention, thecentral lines of the fan shaped X-ray beams may be located on the sameplane, such as the “X-Y” horizontal plane, or on different planes.

Note that, as to the multiple collimators of the present invention, theymay be located on one side of the electron beam E, or on both sides ofthe electron beam E, respectively.

Note that, as to the multiple collimators of the present invention,their positions are symmetrical with respect to a plane passing throughthe target point and perpendicular to the electron beam E.

Note that, as to the multiple collimators of the present invention, thepositions thereof are symmetrical with respect to the electron beam E.

Note that, in the above description of the present invention, theelectron accelerator 1 may produce a high energy electron beam E ofabove 2 MeV in a single amount of energy, or may be a double/multipleenergy electron accelerator generating different energy quantities atdifferent timings. In this case, in addition to obtaining differentenergy quantities in different spaces, it is also possible to obtainX-ray beams having different energy quantities at different timings inthe present invention, and in general, to obtain X-ray beams havingmultiple energy quantities due to spatial and temporal difference.

Embodiments

(System Construction)

As shown in FIG. 1, FIG. 3, FIG. 5, FIG. 7, FIG. 8, the apparatus forgenerating a planar fan shaped high energy X-ray beam having uniformintensity comprises a high energy electron accelerator 1 and a shieldingand collimating device 2. The electron accelerator 1 comprises electronemission unit 101, electron acceleration unit 102, electron driftsegment 104 and target 103. The electron emission unit 101 is mounted atthe front end of the electron acceleration unit 102. The electron driftsegment 104 is mounted on the back end of the electron acceleration unit102 to connect the electron acceleration unit 102 with the target 103.The electron accelerator 1 with 9 MeV energy may produce an X-ray beamhaving a maximum intensity of 3000 Rad/m·min. The shielding andcollimating device 2 comprises shielding structure 201 and multiplecollimators 202 a, 202 b, 202 c, 202 d. The shielding structure 201surrounds the target 103 and is made of lead. The shielding structure201 is thick enough in various directions, such that the intensity ofX-rays may be attenuated by an order of above 10³ in various directions.The shielding structure 201 is formed by multiple blocks to facilitatefabrication and assembly thereof. Collimators 202 a, 202 b, 202 c, 202 dare planar fan gaps arranged in different positions in the shieldingstructure 201. All of the planes where the fan gaps locate pass throughthe target point o and are perpendicular to the pager surface shown inFIG. 8. All of these fan gaps has a thickness of 2 mm, and take thecenter point of the fan as the target point o. All those fans have theircenter lines on the “X-Y” horizontal plane and have a fan opening angleof 90°. The collimator 202 a forms an angle θ1 of 45° with the electronbeam E, the collimator 202 b forms an angle θ2 of 135° with the electronbeam E, the collimator 202 c forms an angle θ3 of −60° with the electronbeam E, and the collimator 202 d forms an angle θ2 of −90° with theelectron beam E.

(Operation Principle)

The electron accelerator 1 is under the actuation of an auxiliary system(for example, a power supply and a control system), and the electronemission unit 101 produces an electron beam E, which enters into theelectron acceleration unit 102 and is accelerated to a high energyelectron beam E, for example an electron beam E of 9 MeV. The highenergy electron beam E passes through the electron drift segment 104 andbombards the target 103 to produce X-rays having an intensitydistribution over various directions in space as shown in FIG. 3. Mostof the X-rays are shielded and absorbed by the shielding structure 201.Four planar fan-shaped X-ray beams having different characters are drawnout from collimators 202 a, 202 b, 202 c, 202 d, respectively. Theplanar fan-shaped X-ray beam drawn out from collimator 202 a has ahigher energy quantity, a larger central radiation intensity, and largervariations in X-ray intensity in the range of the fan opening angle; theplanar fan-shaped X-ray beam drawn out from collimator 202 b has asmaller energy quantity, a lower central radiation intensity, andsmaller variations in X-ray intensity in the range of the fan openingangle; the planar fan-shaped X-ray beam drawn out from collimator 202 chas a medium energy quantity, a moderate central radiation intensity,and smaller variations in X-ray intensity in the range of the fanopening angle; and the planar fan-shaped X-ray beam drawn out fromcollimator 202 d has a smaller energy quantity, a lower centralradiation intensity, and no variation in X-ray intensity in the range ofthe fan opening angle.

The apparatus for generating a planar fan-shaped high energy X-ray beamhaving uniform intensity of the present invention may be used in anX-ray fluoroscopy imaging system. Two inspection channels may bearranged on upper and lower sides (with respect to the description ofFIG. 8(F)) in parallel with the electron beam E. In the upper channel,collimators 202 a and 202 b provide two X-ray beams having differentangles of views and having significant variations in X-ray energy andintensity to achieve the effect of double-energy inspection; and in thelower channel, collimators 202 c and 202 d provide two X-ray beamshaving different angles of views and without significant variations inX-ray energy and intensity to achieve the effect ofdouble-angles-of-views inspection. Applying the present invention in anX-ray fluoroscopy imaging system and using a low cost conventional highenergy electron accelerator as an X-ray source, multiple functions suchas improved image quality, increased inspection speed, increasedlayering information of images, and increased capability of recognizingimaged materials are achieved.

Advantage Effects

The present invention mainly provides an apparatus for generating aplanar fan-shaped high energy X-ray beam having uniform intensity.Through arranging the collimator in a direction forming a lager anglewith the direction of the electron beam shooting the target, a X-raybeam may be obtained with better quality, such as (1) more uniformintensity of X-rays in various directions within a fan area on a plane;(2) the smaller energy dispersion of X-rays within the fan area on theplane; and (3) a smaller size projection point of X-rays target point onthe plane. These three properties may improve the image quality of theX-ray fluoroscopy imaging system. Due to better uniformity of X-rays,X-rays may be drawn out at a large angle to increase X-ray coveragewithin a closer distance. Multiple collimators are arranged in theshielding and collimating device, with different angle and positionrelationships, so as to realize: (1) obtaining multi-angles-of-viewsimages from multiple angles of views; (2) obtaining double-energy effectby means of generating X-ray beams with different energy quantities fromdifferent collimators, so as to determine materials of objects underinspection; (3) implementing a double-channel inspection system usingone accelerator to improve the inspection speed of the X-ray fluoroscopyimaging system and its cost performance; and a combination thereof toform an X-ray fluoroscopy imaging system in different combinations ofdouble channel/high energy/multiple angles of views.

As described above, embodiments of the present invention have beendescribed as such. However, the present invention is not limited theretoand various variations may be made to them. It should be understood thatall of these variations that are made under the technical concept of thepresent invention shall be encompassed in the scope of the presentinvention.

What is claimed is:
 1. An X-ray generating apparatus, comprising: anelectron accelerator including an electron acceleration unit, anelectron emission unit, and a target; and a shielding and collimatingdevice, including a shielding structure and multiple collimatorsarranged in the shielding structure, wherein the target is surrounded bythe shielding structure, the collimators are thin gaps extending fromthe target to an exterior surface of the shielding structure and havingan axis transverse an electron beam shooting the target, and at leasttwo collimators forming different angles with the electron beam arearranged on the same side of a plane contains the electron beam shootingthe target, and the planes where the collimators locate form angles from30 degrees to 150 degrees with the electron beam shooting the target, todraw out planar beams having different draw-out angles, each havinguniform intensity distribution in its respective plane, wherein theplanar beams have energy difference therebetween.
 2. The X-raygenerating apparatus according to claim 1, wherein, the electronaccelerator has energy of above 2 MeV.
 3. The X-ray generating apparatusaccording to claim 1, wherein, each of the collimator is a planarfan-shaped gap arranged in the shielding structure.
 4. The X-raygenerating apparatus according to claim 1, wherein, the electronaccelerator further comprises an electron drift segment connectedbetween the electron acceleration unit and the target.
 5. The X-raygenerating apparatus according to claim 4, wherein, the electron driftsegment is a small diameter conduit, wherein the small diameter conduithas an inner diameter larger than the diameter of the electron beam andan outer diameter less than the outer diameter of the electronacceleration unit.
 6. The X-ray generating apparatus according to claim1, wherein, the shielding structure is made from a material that is ableto block and absorb most of undesired X-rays.
 7. The X-ray generatingapparatus according to claim 1, wherein, the target is a planerstructure, a spherical surface structure, or other curved surfacestructure.
 8. The X-ray generating apparatus according to claim 1,wherein, the positions of the multiple collimators are symmetrical withrespect to a plane passing the target point and perpendicular to theelectron beam.
 9. The X-ray generating apparatus according to claim 1,wherein, the shielding and collimating device consists of twocollimators in a direction forming an angle less than 90° with saidelectron beam and in a direction forming an angle larger than 90° withsaid electron beam, to draw out two planar fan-shaped beams, each havinguniform intensity distribution in its respective plane, wherein the twoplanar fan-shaped beams have energy difference therebetween.
 10. AnX-ray fluoroscopy imaging system, comprising: an X-ray generatingapparatus, having: an electron accelerator including an electronacceleration unit, an electron emission unit, and a target; and ashielding and collimating device, including a shielding structure andmultiple collimators arranged in the shielding structure, wherein thetarget is surrounded by the shielding structure, the collimators arethin gaps extending from the target to an exterior surface of theshielding structure and having an axis transverse an electron beamshooting the target, and at least two collimators forming differentangles with the electron beam are arranged on the same side of a planecontains the electron beam shooting the target, and the planes where thecollimators locate form angles from 30 degrees to 150 degrees with theelectron beam shooting the target, to draw out planar beams havingdifferent draw-out angles, each having uniform intensity distribution inits respective plane, wherein the planar beams have energy differencetherebetween.